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I used to use QO but moved over to DTG as (a)I preferred the look and feel and (b) felt it offered more. Haven't tried QO again as I'm more than happy with what DTG provides.
 
I have Quick Office and have used Docs to Go in the past as well. Quick Office isn't bad, I'm just bummed I didn't go with the 10 dollar version to get dropbox support.
 
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